Ground the center lug on the flipper coil - if it fires, you have a bad ground. check the ground strap from the head to the body. Make sure the SDB has two screws grounding it out.

Check the EOS - must be adjusted to "normally closed" - Clean and regap if necessary

Check the flipper cabinet switches - file and adjust

Check J1 on the SBD and the relay - look for dry joints.